Linux Storage and Filesystem workshop, day 1 [LWN.net]

Linux Storage and Filesystem workshop, day 1

Posted Apr 8, 2009 1:11 UTC (Wed) by ewan (guest, #5533)
In reply to: Linux Storage and Filesystem workshop, day 1 by dberkholz
Parent article: Linux Storage and Filesystem workshop, day 1

I'd have thought the usual approach to that would be to export the
read-only base and the host specific overlay and unify them on the
client, not union mount the two on the server and export the result.

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Linux Storage and Filesystem workshop, day 1

Posted Apr 8, 2009 4:50 UTC (Wed) by jamesh (guest, #1159) [Link]

If the union is done on the client, then modifying to a file stored in the base layer would involve reading the file contents over the network, then writing it back to the server over the network again.

A union performed on the server would only result in local IO when copying the file between layers.

I'm not sure how much of a difference this would make though, since it'd only really hit renames of files in the base layer or partial modification of files. Neither the "truncate and overwrite" or "write to a temporary file and rename over old" methods of writing files would show much difference between server and client side unions.